go - Example code for testing the filesystem in Golang

Question

I'm trying to write a unit test for a function that will interact with the filesystem and I'd like to be able to mock the filesystem during testing.

The code below was given as the answer to this question, where you would create a filesystem interface to use during testing, but I'm new to Go and am struggling to figure out how to use it.

Would someone be able to provide an example of how this interface would be used in a test please?

var fs fileSystem = osFS{}

type fileSystem interface {
    Open(name string) (file, error)
    Stat(name string) (os.FileInfo, error)
}

type file interface {
    io.Closer
    io.Reader
    io.ReaderAt
    io.Seeker
    Stat() (os.FileInfo, error)
}

// osFS implements fileSystem using the local disk.
type osFS struct{}

func (osFS) Open(name string) (file, error)        { return os.Open(name) }
func (osFS) Stat(name string) (os.FileInfo, error) { return os.Stat(name) }

Answer 1

Waitting for answers